<?php
 global $db;
// require("../config/db.php");
 global  $error1,  $error2, $error3, $error4;
$full_name = $username = $password = "";


if(isset($_POST['submit'])){
    $username = $_POST['username'];
    $ad_password = $_POST['password'];
    $full_name = $_POST['full_name'];

    $sql_query = mysqli_query($db, "SELECT username FROM admin WHERE username = '{$username}' ");
    $count = mysqli_num_rows($sql_query);

    $sql_salt = mysqli_query($db, "SELECT randSaltPass FROM admin");
    $row = mysqli_fetch_array($sql_salt);
    $salt = $row['randSaltPass'];
    $password = crypt($ad_password, $salt);

    if(!empty($username) && !empty($ad_password) && !empty($full_name)){

        if($count > 0){
            $error1 = "<div class='alert alert-danger'>
                  <a href='#' class='close' data-dismiss='alert' aria-label='close'>&times;</a>
                  Username  Already Exists.
                </div>";
        }else{

         $u_name     = mysqli_real_escape_string($db, $username);
         $pass_word  = mysqli_real_escape_string($db, $ad_password);
         $admin_name     = mysqli_real_escape_string($db, $full_name);

          if(!preg_match('/^[a-zA-Z]*$/', $u_name)){

             $error2 ="<div class='alert alert-danger'>
              <a href='' class='close' data-dismiss='alert' aria-label='close'>&times;</a>
                   Only Leters are Allowed  For Username.
             </div>";
          }
          if(!preg_match('/^[a-zA-Z]*$/', $admin_name)){
             $error3 ="<div class='alert alert-danger'>
              <a href='' class='close' data-dismiss='alert' aria-label='close'>&times;</a>
                   Only Leters are Allowed  For Fullname.
             </div>";
          }

          if(!preg_match('/^S*(?=S{7,15})(?=S*[a-z])(?=S*[A-Z])(?=S*[d])S*$/', $pass_word)){
            $error4 ="<div class='alert alert-danger'>
              <a href='' class='close' data-dismiss='alert' aria-label='close'>&times;</a>
                  Password Must Be Between 7 and 15 Characters and Must Contain At Least One Lowercase Letter one uppercase Letter and One Digit.
             </div>";
          }


          if((preg_match('/^[a-zA-Z]*$/', $u_name)) && (preg_match('/^[a-zA-Z]*$/', $admin_name)) && (preg_match('/^S*(?=S{7,15})(?=S*[a-z])(?=S*[A-Z])(?=S*[d])S*$/', $pass_word))){


             $sql = "INSERT INTO admin(username, password, admin_name) VALUES('{$u_name}', '{$password}', '{$admin_name}' )";

             $query = mysqli_query($db, $sql);

             if(!$query){
                die("QUERY FAILED " . mysqli_error($db));
             }

          }


        }

    }else{

        if(empty($username)){
            $error2="<div class='alert alert-danger'>
          <a href='' class='close' data-dismiss='alert' aria-label='close'>&times;</a>
               Username Can Be Empty.
           </div>";
        }
        if(empty($full_name)){
            $error3="<div class='alert alert-danger'>
          <a href='' class='close' data-dismiss='alert' aria-label='close'>&times;</a>
               Fullname Can Be Empty.
           </div>";
        }
        if(empty($password)){
            $error4="<div class='alert alert-danger'>
          <a href='' class='close' data-dismiss='alert' aria-label='close'>&times;</a>
                Password Can Be Empty.
           </div>";
        }

    }

}



 ?>

<?php


class Admin_Login
{
    private $_username;
    private $_password;

    public function __construct($c_username, $c_password) {
        $this->_username = $c_username;
        $this->_password = md5($c_password);

        //  $sql_salt = mysqli_query($db, "SELECT randSaltPass FROM admin");
        // $row = mysqli_fetch_array($sql_salt);
        // $salt = $row['randSaltPass'];
        // $password = crypt($db, $salt);
    }

    public function AdminLogin() {
        global $db;

        //Start session
        session_start();

        //Array to validate errors
        $error_msg_array = array();

        //Error messages
        $error_msg = FALSE;

        if($this->_username == "") {
            $error_msg_array[] = "Please input your username";
            $error_msg = TRUE;
        }

        if($this->_password == "") {
            $error_msg_array[] = "Please input your password";
            $error_msg = TRUE;
        }

        if($error_msg) {
            $_SESSION['ERROR_MSG_ARR'] = $error_msg_array;
            header("location: http://localhost/voting_system/sandbox/index.php");
            exit();
        }

        $sql = "SELECT * FROM admin WHERE username = ? AND password = ? LIMIT 1";
        if(!$stmt = $db->prepare($sql)) {
            echo $stmt->error;
        } else {
            $stmt->bind_param("ss", $this->_username, $this->_password);
            $stmt->execute();
            $result = $stmt->get_result();
        }

        if($result->num_rows > 0) {
            //Login successful
            $row = $result->fetch_assoc();

            //Create session
            session_regenerate_id();
            $_SESSION['ADMIN_ID']   = $row["id"];
            $_SESSION['ADMIN_NAME'] = $row["name"];
            session_write_close();

            header("location: http://localhost/voting_system/sandbox/admin_page.php");

        } else {
            //Login failed
            $error_msg_array[] = "The username and password you entered is incorrect.";
            $error_msg = TRUE;

            if($error_msg) {
                $_SESSION['ERROR_MSG_ARR'] = $error_msg_array;
                header("location: http://localhost/voting_system/sandbox/index.php");
                exit();
            }
            $stmt->free_result();
        }
        $result->free();
        return $result;
    }
}

<?php
//Include database connection
require("../../config/db.php");

//Include class Admin_Login
require("../classes/Admin_Login.php");

if(isset($_POST['submit'])) {

    //Create variable to store post array values
    $username = trim($_POST['username']);
    $password = trim($_POST['password']);

    $adminLogin = new Admin_Login($username, $password);
    $rtnAdminLogin = $adminLogin->AdminLogin();

}